Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a nacelle rotatably supported on the tower, a generator and gearbox housed in the nacelle, and one more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles, and transmit the kinetic energy through rotational energy to turn a shaft that couples the rotor blades to the gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid. With the growing interest in wind generated electricity, considerable efforts have been made to develop wind turbines that are reliable and efficient.
A wind turbine comprises several mechanical and electrical components that generate heat energy losses during their operation. These components include, for example, the gearbox (if provided) and generator that are typically housed in the nacelle. Other heat-generating components may be housed in the tower. For example, a converter and a transformer are typically located in the tower and are utilized to feed electrical energy converted from the mechanical energy of the rotor via the generator into the grid. In addition, one or more controllers for controlling operation of the wind turbine are typically arranged within the tower.
Due to the increased performance and size of modern wind turbines, effective cooling of the above-mentioned components is increasingly difficult, particularly with respect to the heat-generating components within the tower. For example, it has been estimated that for a converter control system operating in a 1.5 MW turbine, about 60 kW is dissipated in heat by the converter. Placement of the converter within the turbine tower without adequate cooling can result in a significant temperature rise within the tower, which may be detrimental to the control system and other components within the tower.
Typically, the heat-generating components in the tower are arranged within a cooling airstream generated by fans. The components may include a heat sink that collects the generated heat, with the heat sink placed directly in the airstream. The heated air rises in the tower and is typically exhausted through vents near the top of the tower. The tower may include additional vents, for example in the tower entry door, to allow the passage of outside air into the lower portion of the tower. However, even with this type of arrangement, it is often difficult to feed enough external air into the tower for sufficient cooling of the components.
In addition, restrictions on tower cooling may also result from geographic location of the wind turbines. For example, offshore and near-shore sites generally do not rely on external air as a cooling medium due to the high salt content and humidity of the air, which would result in a corrosive environment within the tower. These sites use an isolated cooling system, such as an air conditioning system with a heat exchanger. A dehumidifier may also be utilized. Humidity and external temperature are considerations that may significantly limit the available cooling options in a given geographical location.
Accordingly, there exists a need for an improved system and method for cooling components within a wind turbine tower that utilizes the cooling capacity of external air yet controls humidity in the structure within acceptable limits.